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Posted 6 Jan 2007


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Examples to create your Conferencing System in .NET, C# VOIP & Video Conferencing Systems using H.323 and TAPI 3

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31 Jan 2007CPOL3 min read
Four examples to create your Conferencing System in .NET using H.323 and TAPI 3

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I noticed that there are many members who want to know how to create an Audio/Video Conferencing System using .NET. We know that there isn't any managed class that supports audio or video streaming in .NET, so I decided to write some applications that can help in writing your conferencing application. From time to time, you will find new examples and tutorials on VoIP, Video Conferencing and Network Programming on my site and also in our Forums that specialize in Network Programming and VoIP.

Introduction to H.323

H.323 is an umbrella recommendation from the ITU-T, that defines the protocols to provide audio-visual communication sessions on any packet network. It is currently implemented by various Internet real-time applications such as NetMeeting and Ekiga (the latter uses the OpenH323 implementation). It is a part of the H.32x series of protocols which also addresses communications over ISDN, PSTN or SS7. H.323 is commonly used in VoIP, Internet Telephony, or IP Telephony and IP-based videoconferencing. For more information about H.323, see Internet Telephony with H.323 on MSDN.

Introduction to TAPI 3 Telephony

TAPI version 3 is a COM-based API that merges classic and IP telephony. Possible applications range from simple voice calls over the Public Switched Telephone Network (PSTN) to multicast multimedia IP conferencing with quality of service (QOS).

There are four major components to TAPI 3:

  1. COM API
  2. TAPI Server
  3. Telephony Service Providers (TSPs)
  4. Media Stream Providers (MSPs)

The API is implemented as a suite of Component Object Model (COM) objects. Moving TAPI to the object-oriented COM model allows developers to write TAPI-enabled applications in many languages, such as .NET, Java, or C++. Use of COM enables component upgrades of TAPI features.

The COM-based telephony API, TAPI 3.x, is available starting with Microsoft Windows X. TAPI 3.x provides greatly enhanced development tools for the modern world of communication programming, where a "call" may be a video stream on an IP-based network, and there is no phone set involved in the session.

Sample image

Generally speaking, application writers will find that TAPI 3.x provides better support to implement flexible communications controls. For more information, see Telephony Integration and Conferencing on MSDN.

Introduction to RTP

RTP - Real Time Transport Protocol is an Internet protocol for transmitting real-time data such as audio and video. RTP itself does not guarantee real-time delivery of data, but it does provide mechanisms for sending and receiving applications to support streaming data. Typically, RTP runs on top of the UDP protocol, although the specification is general enough to support other transport protocols that know how Windows supports Real Time Communication. See this RTCP API article.

RTP Header

RTP Header


  • V indicates the version of RTP used
  • P indicates the padding, a byte not used in the bottom packet to reach the parity packet dimension
  • X is the presence of the header extension
  • CC field is the number of CSRC identifiers following the fixed header. CSRC field are used, for example, in conference case
  • M is a marker bit
  • PT is the payload type

My Projects

Example 1: Voice Conferencing Using OPEN H.323 Library

In this example, I used the Openh323 ocx to create H.323 Voice Chat - it's very easy to use.


Example 2: Voice Conferencing Using TAPI3.DLL

In this example, I used TAPI3 to create audio conferencing, For more information, see Rendezvous Code Examples on MSDN.

TAPI 3 Voice Conference

Example 3 and 4: Peer-to-Peer Video Voice Chat

In this example, I used the Wave Library to capture and send voice through the network and I used the Stream classes to transfer captured video images from a camera.

Peer-Peer Conerence System

In this other example, I used the avicap32.dll API to capture the camera image. You can also use this example to capture from any other capturing device such as a TV Tuner and then you can send it through the network.

Sample image


In this article, I have just posted some examples that will help you to start creating your conferencing system. I will explain the technical code description in other articles.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Fadi Abdelqader
Systems Engineer SocketCoder.Com
Jordan Jordan
Fadi Abdelqader
Facebook Group:
Facebook Page:

Last Published Book:
-Professional Network, Distributed Systems & TCP/IP Programming In .NET Framework 1.1 & 2.0 (2006 Release)

Last Published eBook:
- The SocketCoder e-Reference For Network, Distributed Systems And TCP/IP Programming In .NET, Arabic (SocketCoder.Com 2010)

Last Projects:
- Silverlight Based Projects For Web Video Conferencing (WCS,WMS,WCS Plus..)
-(SocketCoder) RTP Multicasting VOIP Library
-(SocketCoder) Remote Controlling Systems

Last SocketCoder RSS:

Comments and Discussions

PraiseThanks Pin
Member 1404839510-Jan-19 21:36
MemberMember 1404839510-Jan-19 21:36 
QuestionNullReferenceException in Peer to Peer full duplex voice chat. Pin
Member 1313698419-Apr-17 7:26
MemberMember 1313698419-Apr-17 7:26 
AnswerRe: NullReferenceException in Peer to Peer full duplex voice chat. Pin
florisprinsloo31-May-17 23:19
Memberflorisprinsloo31-May-17 23:19 
QuestionHow to GetCallInformation and Transfer call In with c# ? Pin
Jignesh Patel 42827-Nov-16 1:16
MemberJignesh Patel 42827-Nov-16 1:16 
QuestionIs there VCS example? Pin
roni_mn25-Oct-16 0:11
Memberroni_mn25-Oct-16 0:11 
Questionhow to save captured image and video from webcam using c# Pin
roddam harini4-Sep-15 0:22
Memberroddam harini4-Sep-15 0:22 
Questionhow it possible that your project wotk? Pin
knuzich12-Jul-15 23:35
Memberknuzich12-Jul-15 23:35 
QuestionErrors when built Pin
Member 1136014827-Jan-15 2:56
MemberMember 1136014827-Jan-15 2:56 
GeneralMy vote of 4 Pin
Mic6-Aug-13 15:27
MemberMic6-Aug-13 15:27 
GeneralMy vote of 3 Pin
tambadesachin21-May-13 2:16
Membertambadesachin21-May-13 2:16 
QuestionWhat is the easiest way to test the H323 VOIP sample povided Pin
Member 977473320-Feb-13 18:19
MemberMember 977473320-Feb-13 18:19 
QuestionIVR Voice Navigation Pin
Niko6825-Sep-12 3:23
MemberNiko6825-Sep-12 3:23 
QuestionSending text,image,voice from c# apps to Java Pin
AINJALIL8830-Aug-12 4:05
MemberAINJALIL8830-Aug-12 4:05 
GeneralExcellent Pin
albhadly25-Aug-12 3:24
Memberalbhadly25-Aug-12 3:24 
QuestionOlder DLL's and the VS 2010 on 64bit... Pin
yetanotheruser928-Jun-12 1:00
Memberyetanotheruser928-Jun-12 1:00 
AnswerRe: Older DLL's and the VS 2010 on 64bit... Pin
Banjoo15-Jul-12 1:48
MemberBanjoo15-Jul-12 1:48 
AnswerRe: Older DLL's and the VS 2010 on 64bit... Pin
Artebin29-May-14 11:12
MemberArtebin29-May-14 11:12 
GeneralMy vote of 5 Pin
manjukgowda11-Apr-12 3:20
Membermanjukgowda11-Apr-12 3:20 
Bugabout video conferencing Pin
rakeshnagarshyam23-Mar-12 9:35
Memberrakeshnagarshyam23-Mar-12 9:35 
Questionh323 323 Voice example Pin
flor_jim11-Mar-12 14:57
Memberflor_jim11-Mar-12 14:57 
QuestionIf it support Wince or Win Mobile? Pin
mahaofan@gmail.com9-Feb-12 22:32
Membermahaofan@gmail.com9-Feb-12 22:32 
QuestionThanks!! Pin
IronWolf193-Feb-12 20:50
MemberIronWolf193-Feb-12 20:50 
QuestionSEHException was unhandled External component has thrown an exception. Framework 2 to 4 Pin
Auntpol27-Nov-11 7:21
MemberAuntpol27-Nov-11 7:21 
GeneralNo connection could be made because the target machine activity refused it Pin
Member 408286014-May-11 18:15
MemberMember 408286014-May-11 18:15 
GeneralRe: No connection could be made because the target machine activity refused it Pin
Member 1139748423-Jan-15 20:44
MemberMember 1139748423-Jan-15 20:44 

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